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Tuesday, February 13, 2007

The World's Largest Microscope

One of the most amazing things about nature is its diversity. The amount of structures, shapes and colors is just fascinating if you consider that everything is build up from only some few ingredients that we call the particles of the standard model. For a long time in the history of science, progress in physics has been accompanied by an increase of resolution - a fascinating journey in negative powers of ten.

The search for the building constituents of our world has come a long way. Democritus, sometime around 500 BCE1 was the first to theorize that there is a fundamental indivisible entity which he called átomos - the 'uncuttable'. Today we know that what was later termed 'atom' isn't uncuttable at all, but actually mostly empty, the rest being a small core of protons and neutrons, orbited by electrons. And even the protons and neutrons aren't fundamental particles.

The invention of magnifying glasses, and the light microscope was the first step. Roughly spoken, a microscope uses photons that are focused with lenses. These photons are either reflected on, or transverse a sample.

The photons are then caught on a screen, or a film, and give you a picture. The resolution that one can achieve with light is limited by its wavelength. It is impossible to resolve structures finer than that. Using light of higher frequency (gamma rays) increases the resolution. The average microscope allows us to see cells, or the structure of crystals (for some stunning images see here) .

More efficient than using photons is to use focused beams of massive particles. Due to their quantum properties, massive particles also have a wavelength which considerably smaller than that of massless particles like photons. In addition, charged particles like electrons, can be nicely directed by electromagnetic fields. Indeed, magnetic fields can be used for beams of charged particles like lenses. The electromagnetic fields can also be used to accelerate the charged particles. The advantage of this is that faster particles have a higher energy, or equivalently, a smaller wavelength. Therefore, the faster one accelerates a particle, the better the resolution.

Modern electron microscopes can roughly resolve distances as small as an Ångström - that is about the size of an atom.

However, if you hit the sample with particles of higher and higher energies, you'll eventually alter what you want to observe. If the energy gets sufficiently high, electrons will not only elastically scatter from the sample, but the beam will react with the sample to form new particles. Needless to say, the faster the particle, the more complicated it then becomes to reconstruct an image.

A particle accelerator is nothing but a giant microscope.

Particle beams are accelerated to highest energies, and then either crash into a sample (fixed target) or head on into another beam (collider). The particles that come out of the collision are detected. And here the physicist enters the stage and reconstructs particle's trajectories to understand what has happened. The outcome of such collisions depends on the structure of the elementary matter, and from detecting the particle traces one can confirm, or falsify, models about the stuff that we are made of.

It is quite a detective work. Extracting information about the structure of matter from hundreds of scattered particles whose initial motion is only know to a certain precision is like examining the outcome of a car crash, and trying to find out where the driver had dinner the night before. But over the last decades, physicists have become quite good at this. They've even grown a subclass of the species called: high energy physicists.

The February issue of the Discover Magazine has a very well written and researched article 'The Big Bang Machine' by Tim Folger about one of the most interesting currently running experiments, the Relativistic Heavy Ion Collider (RHIC). The article explains the properties of the hot plasma of quarks and gluons that is investigated there, why these findings are so exciting, and what this has to do with string theory and the AdS/CFT correspondence2 (see also our previous posts about the Quark Gluon Plasma and what string theory has to say about it).

The LHC is scheduled to start in September. Its main task is the collision of two proton beams with an energy of roughly 10 TeV, that corresponds to a resolution of 1/1000 femtometer. It will allow us to look closer into the structure of matter than ever before. With this, we hope to finally find the Higgs-particle that is our current explanation how particles get mass. But we also have the possibility to find evidence for supersymmetric partners of the standard model particles, and who knows - maybe quarks turn out to be not elementary particles after all?

Besides the proton-proton collisions, the LHC will also run collisions of heavy ions similar to the ones at RHIC, but with higher energy. Though the single particle's collisons have less energy that in the proton-proton collisions at LHC, using larger clusters of colliding particles with the heavy nuclei one can create blobs of matter with extremely high density and temperature. In such a way, LHC is able to re-create conditions that have not existed since the beginning of the universe. The above mentioned Discover article quotes Bill Zajc from the PHENIX experiment at RHIC:

'One question that screams out to be answered is whether we'll see the same sort of perfect fluid that we see at RHIC'.

If you're not yet totally fascinated by the LHCs prospects you're probably German, so you can have a look at this nice video about the LHC (thanks to Andi). Among other things it shows how the detective's work looks like - and what's essential for it :

However, the protons that are collided at the LHC are themselves made out of three (valence) quarks that are bound together with gluons, also called the 'partons' of the system. So, the detective needs to know something about the distribution of the proton's constituents that is called as the 'parton distribution function'. This complicates matters and increases uncertainties. In addition, this also means that the total energy of the accelerated beams doesn't fully go into the elementary parton collisions, but the energy is actually distributed over these partons. And the energy of the single collisions of these constituents is consequently less.

However. Having told you why this is fascinating and exciting stuff, I'd also like to bring up an issue that is usually not discussed in design reports, and which I was recently reminded of through this article 'Wer soll das bezahlen'- Who's supposed to pay for that? (again in German, unfortunately)

"The only things physicists always have are problems. At least when they try to understand the world. They don't get the most obvious stuff: Why do things have weight? Are there really only three dimensions?"

(if you can, I encourage you to read the comments) whichs bring up the question whether it's justified to spend such an amount of money, while there are still people starving elsewhere in the world.

It is of course a tough question, one that I ask myself repeatedly, being aware of my privileged position in Somewhere, North America. Wouldn't all that money be better used otherwise (like, you could give it to me ;-)). One can ask that about every possible investment a country makes, and to begin with I am perfectly sure there are better places to doubt the wisdom of these decisions. However, taking money and - in a mood of generosity - just giving it to those in need, whether in your own or other countries, sounds like a good idea, but isn't going to help on the long run. The reason is simply that we still can't eat money. Investments are only sensible if they permanently affect the infrastructure. It's not as easy as just scraping some billions here and giving them to the homeless. Whether or not we like the current government, the very purpose of politics is to optimize the use of tax money.

This might sound obvious, but I think it's necessary to point out every now and then, so this is now. Yes, experiments in high energy physics are a luxury of our societies, and we are very lucky that we can afford them today. The world is not a system in equilibrium. It has never been. I doubt it will ever be, but we might be able to get closer than we are now. Working towards equilibrium however isn't done by scraping money here and giving it to somebody else over there. It requires, well, a thoroughly investigated plan as to whether the investment is sensible, and not just a feeling of guilt.

No, building large particle colliders isn't necessary for the survival of our species, but it is the way to answer questions that men have asked since thousands of years. There will always be parts of this world ahead of others. But to close with a quotation by Isaac Asimov:

'There is a single light of science, and to brighten it anywhere is to brighten it everywhere.'

26 comments:

Is it a luxury? Maybe. But it's a luxury as old as mankind itself. The earliest tribes apparently had shamans and mystic men, reading the stars, not contributing directly to the wealth of society in terms of food and shelter.

The curiosity, the need for stories, that is deeply human. The entire ethics of humanity are not based on reducing human suffering (though it is, of course, a central part of it) but also always look for what is beyond.

In other words, humanity contains both, Empathy AND Imagination, and we need both, even though the latter need is much more intangible.

Do you know when the heavy ion collision phase will have its first physics run? And are they going to use the same models and analysis to determine the hydrodynamic parameters of the "fluid" or whatever is seen... or will it be somewhat complementary?

If there are strangelets flying around the universe, then occasionally a strangelet should hit the planet Earth, where it would appear as an exotic type of cosmic ray. This raises the question whether a strangelet from space would convert the whole planet to strange matter. The disaster scenario is this: one strangelet hits a nucleus, catalyzing its immediate conversion to strange matter. This liberates energy, and sends pieces (more strangelets) flying in all directions. These merge with other nuclei and convert them, leading to a chain reaction, at the end of which all the nuclei of all the atoms have been converted, and earth has been reduced to a hot cloud of strangelets.

The general belief is that this would not happen, because most models predict that strangelets, like nuclei, are positively charged, so they are electrostatically repelled by nuclei, and would rarely merge with them.[3] However, concerns of this type were raised at the commencement of the Relativistic Heavy Ion Collider (RHIC) experiment at Brookhaven, which could potentially have created strangelets. A detailed analysis [4] concluded that the RHIC collisions were comparable to ones that naturally occur as cosmic rays traverse the solar system, so we would already have seen such a disaster if it were possible.

In the case of a neutron star, however, the conversion scenario seems much more plausible. A neutron star is in a sense one giant (20 km across) nucleus, held together by gravity. If a strangelet hit a neutron star, it could convert a small region of it, and that region would grow to consume the entire star.[5]

While "fear rules" good thinking, they postulated what these strangelets could be and went with it. How did the idea of micro blackholes serve to help identify further positions about which the beginning of particle showers could have emerged from such collisions, and one wonders about the "perfect fluid." The "quick dissipation of micro blackholes" from cosmic particle collisions?

When the Republican administration has spent over half a trillion dollars on a war of choice, not necessity, in Iraq, then asking for ten billion dollars to advance human knowledge though without practical application does not seem so difficult.

Wouldn't it be better in any case for nations to compete in science and music and art and sports than in armaments and war? Then even appealing to national prestige is a legitimate argument, IMO. The "people starving in another country" is not an argument, because the budget is never going to be diverted to help those people.

yes, thanks, you said that very nicely. With luxury I meant exactly that: it's not necessary for our survival to build the LHC, but it's what makes the difference between surviving and living. What's all the struggle good for if not to reach out for the frontiers of our knowledge?

Hi Clifford,

reg. heavy ion runs at LHC. I don't know. Last thing I heard was that it would be 'desirable' to have a pilot run already in 2007, and the first run sometime 2008, but I couldn't find any sensible information about it.

Wouldn't it be better in any case for nations to compete in science and music and art and sports than in armaments and war?

Wise words. I've always found it would help us getting along if we just had more options before killing each other. See - I don't think humans will ever erase warfare completely, it will always remain the last option to threat other peoples lives and to take with force what couldn't be taken otherwise. But I think we could just add some possible steps before that. E.g. take sports and science in the 'cold war'. Would it have been such a cold war without this competition? We all want to be appreciated, to be special, and to be the best at least in some regards.

I wonder though why, when it comes to global competition, most nations focus on sectors that require enormous financial resources, like technology and military. It might be hard for (financially) poorer countries to compete technologically, but how much does a theoretical physicist cost?

Electrons are enslaved in power grids and circuitry worldwide as you read this. Uncle Al demands electron advocacy! There are way more than twice as many baryons than electrons in Earth. Annihalating electrons is heinous baryonic particleism - leptocide! (Photons are not a privileged minority.)

you write:A person most intense and preoccupied with the endeavours they work, will notice that time passes very quickly around them. It's as if the world bypassed them, as the focus had cost them the appearance or the attention needed to take care of themselves. "Should I care" as I think of them, whether their hair long or that their desk is pile high with paper?

Sounds like a high gamma-factor ;-) Anyway, you know, what makes theoretical physics different from mathematics is that we can't leave out the world. If we let it bypass and get lost in our own sphere of thought, we might grow impressive piles of papers but as physicists we have failed. Regarding the attention to take care of themselves, I have the suspicion that Einstein's legacy weights heavily on many of my male colleagues ;-)

Electrons are monstrously oppressed in power grids. Annual planetary electricity generation is 1.9x10^13 kwh. At 120 V that averages 18 billion amperes 24/7 (including leap years). Every second of every day 10^29 electrons are whipped and trampled. They scream and scream and scream.

K-40 inverse beta-decays. 5.14x10^21 g of Earth's atmosphere is 1.288% argon, 99.6% of that being Ar-40 from K-40 decay. 10^42 electrons did not go home since the Earth was formed. They were annihilated into photons by matter-antimatter cancellation.

B:Regarding the attention to take care of themselves, I have the suspicion that Einstein's legacy weights heavily on many of my male colleagues

I would suspect, as one learns more of the man, one might wonder "what was so great?"

While science progresses from the large to the small things. Vast changes, as to how we saw the world, now holds a vision of the small things as well. Much more dynamical.

How could one progress, if there were no conclusions in cosmology, to improve to the views of astrophysics?

Should the merits of science be attached to the "merits of the man" if they are not beholding to the ethics of the humanitarian? Practise their religions, and live according to the ten Commandments, or Jewish law? Be govern by the "Old One?"

"Extracting information about the structure of matter from hundreds of scattered particles whose initial motion is only know to a certain precision is like examining the outcome of a car crash, and trying to find out where the driver had dinner the night before."

lol! so how was your Valentine's Day - chocolates? and were they filled with liquers or bubbles?

The Large Hadron Collider [LHC] at CERN might create numerous different particles that heretofore have only been theorized. Numerous peer-reviewed science articles have been published on each of these, and if you google on the term "LHC" and then the particular particle, you will find hundreds of such articles, including:

1) Higgs boson

2) Magnetic Monopole

3) Strangelet

4) Miniature Black Hole [aka nano black hole]

In 1987 I first theorized that colliders might create miniature black holes, and expressed those concerns to a few individuals. However, Hawking's formula showed that such a miniature black hole, with a mass of under 10,000,000 a.m.u., would "evaporate" in about 1 E-23 seconds, and thus would not move from its point of creation to the walls of the vacuum chamber [taking about 1 E-11 seconds travelling at 0.9999c] in time to cannibalize matter and grow larger.

In 1999, I was uncertain whether Hawking radiation would work as he proposed. If not, and if a mini black hole were created, it could potentially be disastrous. I wrote a Letter to the Editor to Scientific American [July, 1999] about that issue, and they had Frank Wilczek, who later received a Nobel Prize for his work on quarks, write a response. In the response, Frank wrote that it was not a credible scenario to believe that minature black holes could be created.

Well, since then, numerous theorists have asserted to the contrary. Google on "LHC Black Hole" for a plethora of articles on how the LHC might create miniature black holes, which those theorists believe will be harmless because of their faith in Hawking's theory of evaporation via quantum tunneling.

The idea that rare ultra-high-energy cosmic rays striking the moon [or other astronomical body] create natural miniature black holes -- and therefore it is safe to do so in the laboratory -- ignores one very fundamental difference.

In nature, if they are created, they are travelling at about 0.9999c relative to the planet that was struck, and would for example zip through the moon in about 0.1 seconds, very neutrino-like because of their ultra-tiny Schwartzschild radius, and high speed. They would likely not interact at all, or if they did, glom on to perhaps a quark or two, barely decreasing their transit momentum.

At the LHC, however, any such novel particle created would be relatively 'at rest', and be captured by Earth's gravitational field, and would repeatedly orbit through Earth, if stable and not prone to decay. If such miniature black holes don't rapidly evaporate and are produced in copious abundance [1/second by some theories], there is a much greater probability that they will interact and grow larger, compared to what occurs in nature.

There are a host of other problems with the "cosmic ray argument" posited by those who believe it is safe to create miniature black holes. This continuous oversight of obvious flaws in reasoning certaily should give one pause to consider what other oversights might be present in the theories they seek to test.

I am not without some experience in science.

In 1975 I discovered the tracks of a novel particle on a balloon-borne cosmic ray detector. "Evidence for Detection of a Moving Magnetic Monopole", Price et al., Physical Review Letters, August 25, 1975, Volume 35, Number 8. A magnetic monopole was first theorized in 1931 by Paul A.M. Dirac, Proceedings of the Royal Society (London), Series A 133, 60 (1931), and again in Physics Review 74, 817 (1948). While some pundits claimed that the tracks represented a doubly-fragmenting normal nucleus, the data was so far removed from that possibility that it would have been only a one-in-one-billion chance, compared to a novel particle of unknown type. The data fit perfectly with a Dirac monopole.

While I would very much love to see whether we can create a magnetic monopole in a collider, ethically I cannot currently support such because of the risks involved.

Somebody which I meet at a park here in Geneva, Switzerland where our 2 labradors love to play together, told me today that it looks like during the experiement the CERN is starting this autumn 3 things could happen:

1. If all the calculations where right (and it's the first time we try this) it should give the world a BIG BANG

2. If somethings goes wrong only one of these things (and not both together) could happen:

A black holeJust, depending on its size, sucks us slowly or faster in and could make us changing time zone in a funny way. But finally all this universe would get sucked in.

A wormholeThis means that an unique potential time travel awaiting (please fasten your seatbelt ;-). That actually has a good chance that we will time travel instantly, peacefully and in first class.

Well, OF COURSE I did not believe this person. But I was intrigued. This web site is just to diplay the views and opinions on this issue.

I think he has part of this information from the movie 'The Black Hole' ;-)

Now I understand it's (possibly incomplete list) about a collapse, a wormhole, a strangelet or a black hole

This blog has been completed in 24 hours. Why? Because only a few days are left until the warming up systems status is implemented at the LHT. A few days that may be the last we have.

As I live in Geneva, I would much care if a black hole sucked me in or if I would be on timetravel through the universes if the wormhole comes.

What a post!. Thanks for all this information about all this stuff. I tell you, there is a lot of things, I mean large scale scientific projects, are starting just now. This means a lot of high-level scientific infrastructures as you said.